Hybridization of Atomic Orbitals

Introduction to Hybridization

• Definition: Hybridization refers to the mixing of atomic orbitals to form new hybrid orbitals.
• Analogy: Similar to mixing substances (e.g., salt + water, sugar + water).
• Types of Atomic Orbitals: Typically involves s and p orbitals.

Importance of Studying Hybridization

• Molecular Geometry: Helps to understand the shape of molecules.
• Bonding: Clarifies how atomic orbitals bond in molecules.

Mechanism of Hybridization

• Combines different atomic orbitals of similar energy.
• Example using two types of atoms (A and B) shows that hybridization allows A to form consistent bonds with B through a new hybrid orbital.
  • A can create sp bonds with B, rather than ss or sp bonds which would be inconsistent.

Carbon Hybridization

SP3 Hybridization

• Composition: 1 s orbital + 3 p orbitals = 4 orbitals total.
• Character: 25% s character, 75% p character.
• Example: Carbon in ground state has 6 electrons (2 in 1s, 2 in 2s, 1 in 2px, 1 in 2py).
• Excited State: 2s and three 2p orbitals mix to form 4 hybrid sp3 orbitals, each with 1 unpaired electron.
• Geometry: Tetrahedral arrangement, bond angle of 109.5°.
• Example Molecule: Methane (CH4), formed by sharing unpaired electrons with four hydrogen atoms.

SP2 Hybridization

• Composition: 1 s orbital + 2 p orbitals = 3 orbitals total.
• Character: 33% s character, 67% p character.
• Example: Carbon's ground state has 2s with 2 electrons; excited state has 1 unpaired electron in p orbitals.
• Hybrid Orbitals: 2s, 2px, and 2py combine, with 2pz remaining unhybridized.
• Geometry: Trigonal planar arrangement, bond angle of 120°.
• Example Molecule: Ethene (C2H4) with one pi bond from unhybridized orbitals and sigma bonds from hybrid orbitals.

SP Hybridization

• Composition: 1 s orbital + 1 p orbital = 2 orbitals total.
• Character: 50% s character, 50% p character.
• Excited State: 2s orbital mixes with one 2p orbital, forming 2 sp hybrid orbitals, while the remaining p orbitals are unhybridized.
• Geometry: Linear arrangement, bond angle of 180°.
• Example Molecule: Ethyne (C2H2) with one sigma bond from sp hybrid orbitals and two pi bonds from unhybridized p orbitals.

Summary

• Understanding hybridization is critical for predicting molecular geometry and bonding.
• Different hybridization states (sp3, sp2, sp) correspond to different molecular shapes and bond angles, influencing chemical behavior.